function isset() {
  //  discuss at: http://phpjs.org/functions/isset/
  // original by: Kevin van Zonneveld (http://kevin.vanzonneveld.net)
  // improved by: FremyCompany
  // improved by: Onno Marsman
  // improved by: Rafał Kukawski
  //   example 1: isset( undefined, true);
  //   returns 1: false
  //   example 2: isset( 'Kevin van Zonneveld' );
  //   returns 2: true

  var a = arguments,
    l = a.length,
    i = 0,
    undef;

  if (l === 0) {
    throw new Error('Empty isset');
  }

  while (i !== l) {
    if (a[i] === undef || a[i] === null) {
      return false;
    }
    i++;
  }
  return true;
}